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Thursday

The Hows And Whys Of Itching Explained

We all had those moments when an irresistible itch just happens to ignite at the exact time the series' episode we are watching reaches its climax. The vicious itch leaves us with two choices: Either we try to relieve it by scratching and risk missing our favorite TV show's best moments, or we simply resist the urge and call it a day. Oftentimes, this dilemma feels like having to choose between being killed by a firing squad or being burned at stake.

But what does science have to tell us about this unpleasant sensation?

Once believed to be a slight version of pain, recent studies have shown that pain and itch are two completely separate sensations. A 2013 study published in Science, found that the itch reflex is triggered by a chemical called Nppb, which is produced by specialized neurons. The researchers were able to test Nppb's role in the itching behavior either by using mice that were genetically modified to lack in Nppb, or by giving them a neurotoxin that blocked Nppb's receptors. The results showed that the altered mice did not exhibit any itch responses, although they still retained their ability to sense pain and heat.

While that may explain the mechanisms that fire the itch chain reaction, it still doesn't tell us anything about why this sensation occurs in the first place. It all starts in the skin, at least for the mechanical itch. A relatively recent scientific study that was published on October 30 2015 in the journal Science, has shed light on how our bodies respond to external stimulus by triggering the itching behavior. Basically, our spine contain a set of spinal inhibitory interneurons, which are cells that act as a postman between the skin and the brain. So when a bug lands on our skin, chances are that these cells will transmit this signal to our brain, which in turn activates our body's typical itch response (i.e., scratching our skin).

Although the aforementioned studies have focused on the physical side of itching, researchers from Washington University School of Medicine in St. Louis, have recently uncovered that there is at least a psychological dimension to this behavior, as is the case in socially contagious itching. Using mice, the scientists identified a chemical called GRP (gastrin-releasing peptide), which is responsible for making a mouse feel itchy after seeing a video of other mice scratching. The findings suggest that socially contagious itching is far from being just a psychological reaction. In fact, it is quite the opposite. So next time you start scratching after seeing others doing it, remember that this behavior is so entrenched in our biology it can be classified as a hardwired response!